Intermittant non-SKS remote unlock

Hi All,
I've had this problem twice now, and concerned it might get worse. After leaving the car locked over night the remote unlock (pressing the unlock key on the remote) has no effect at all, on either my original nor virtually-new remote. Then a few minutes later everything is fine and stays fine for several months.

This morning I had to open the driver's door with the mechanical key, and the alarm of course went off, but stopped as soon as the car got to "READY", and is now fine again.
12V battery voltage looks fine (not great, but okay) and no other odd behaviour. (Oh, except the radio doesn't come on in high temps unless "tapped")

Normally the main remote will operate the locks from a hundred feet away. Even when it's not working the red light on the fob flashes as normal. I haven't checked the dashboard key light...

Given that minutes later it's all working fine it can't be the remote access switch.

Does anyone know where the pickup for the RF signal is? I wonder if that's damaged in some way. It's been first thing in the morning both times, so I wonder if the low temp is causing it.

Cheers!
Jon

 

Thanks for the input guys. I know the 12v battery has been in there a long time, and not quite as high voltage as it should, so maybe this is the cause.

I thought (from a friend in the auto electronics design business) that all automotive spec kit had to operate correctly down to some ridiculous low voltage, like 5v for this very reason.
I'm aware of all the stories of strange behaviour with a suspect 12v battery that goes away as soon as the battery is replaced, but I just find it hard to believe that there is any 12v electronics in there at all, and that the voltage regulators don't have more than enough headroom to handle one volt drop at the 12v battery.

Actual digital electronics inside the car is likely running on 3.3v or even 2.5v, so there must be some converter/regulator in there, which wouldn't care about 12.9v versus 11.5v